The objective of the proposed program is to gain increased understanding of the neural mechanisms which underlie hearing through an integrated series of studies: 1) determination of the mechanical vibration patterns of the basilar membrane in the squirrel monkey using both the Mossbauer technique and laser interferometry: 2) measurement of the electrical impedance between the scala media and a remote electrode in the guinea pig; 3) anatomical and electrical recording studies on the organ of Corti of the newborn mouse in tissue culture; 4) recordings from single auditory nerve fibers in the cat responding to simple tones, complex tones and speech-like sounds; 5) recordings from single neurons in the cochlear complex of the cat to assess both cochlear output and the transformations imposed by neurons in the complex on information received from auditory nerve fibers; 6) mathematical modeling of the vibratory properties of the basilar membrane and the excitatory process in the hair cell; 7) anatomical and unit recording studies on the organization of auditory cortex in the monkey. Multidisciplinary methods are used, including microelectrode recording techniques with special emphasis on study of the coding of auditory stimulus information in the temporal discharge patterns of single neural units. Computers are used extensively in controlling the parameters of auditory stimuli, in the collection and analysis of physiological data, and in mathematical modeling. Histological identification of recording sites and cytoarchitectonic studies are performed; anatomical methods include tract-tracing techniques, autoradiography, and scanning and transmission electron microscopy. BIBLIOGRAPHIC REFERENCES: Gibson, M.M., Hind, J.E., Kitzes, L.M. and Rose, J.E. Estimation of traveling wave parameters from the response properties of cat AVCN neurons. In: Evans, E.F. and Wilson, J.P. (Eds.) Psychophysics and Physiology of Hearing, Academic Press, London, 1977, in press. Geisler, C.D., Mountain, D.C., Hubbard, A.E., Adrian, H.O. and Ravindran, A. Alternating electrical-resistance changes in the guinea-pig cochlea caused by acoustic stimuli. J. Acoust. Soc. Amer., 1977, in press.